Shutter structure and mixing tube assembly for gas burner

ABSTRACT

Shutter comprises a C-shaped band of resiliently flexible metal frictionally engaged around the portion of a mixing tube having primary air inlets, the edges of the band and an aperture therein defining openings adjustably registrable with the inlets by turning the band. One edge of the band is turned inwardly to form stops which limit turning and axial movements thereof. Circumferential terminal portions of the band adjacent its ends are curved outwardly to glide over edges of the inlets.

United States Patent 1 91 Ferlin et al.

[451 Sept. 16, 1975 SHUTTER STRUCTURE AND MIXING TUBE ASSEMBLY FOR GAS BURNER [75] Inventors: William J. Ferlin; Nelson G. Mayer,

both of Detroit, Mich.

[73] Assignee: Lincoln Brass Works, Inc., Detroit,

Mich.

[21 Filed: May 9,1974

21 Appl. No.: 468,224

[52] US. Cl. 431/354; 48/180 F [51] Int. Cl. F23D 13/40 [58] Field of Search 431/354, 355; 48/180 F,

[56] References Cited UNITED STATES PATENTS 2/1922 Corkell 431/355 8/1929 Bandoly etal ..431/3s5 11/1967 Ward 48/180F Primary Examiner-Carroll B. Dority, Jr. Attorney, Agent, or Firm-Bames, Kisselle, Raisch & Choate ABSTRACT Shutter comprises a C-shaped band of resiliently flexible metal frictionally engaged around the portion of a mixing tube having primary air inlets, the edges of the band and an aperture therein defining openings adjustably registrable with the inlets by turning the band. One edge of the band is turned inwardly to form stops which limit turning and axial movements thereof. Circumferential terminal portions of the band adjacent its ends are curved outwardly to glide over edges of the inlets.

11 Claims, 5 Drawing Figures SHUTTER STRUCTURE AND MIXING TUBE ASSEMBLY FOR GAS BURNER This invention relates generally to a mixing tube by which a mixture of fuel gas and air is furnished to a gas burner typically of the type employed in domestic gas ranges. More particularly, the invention involves an assembly of a mixing tube and a shutter which is operable to adjust the effective size of primary air inlets in the mixing tube.

The conventional mixing tube has an upstream end which receives fuel gas from a source such as a valve or conduit, primary air inlets adjacent the upstream end, and a Venturi downstream of the primary air inlets. The fuel gas-primary air ratio is regulated by adjusting the effective size of the primary air inlets. Conventionally, the adjustment is accomplished by a shutter which is tumable relative to the mixing tube to close portions of the inlets. The shutter is anchored in adjusted position by a screw which passes through slotting in the shutter and is threaded into an opening in the mixing tube wall.

The conventional structure thus requires a screw as a separate part and separate machining and assembly operations such as drilling and tapping a hole in the mixing tube wall, aligning the shutter slot with the hole, and running the screw into the hole. These requirements add objectionably to the cost of mixing tube and shutter assemblies which typically must be made very inexpensively. Moreover, the primary air inlets in a mixing tube are usually formed by stamping which leaves rough, sharp edges tending to impede turning of the conventional shutter for adjustment purposes.

The object of the present invention is to provide shutter structure and a mixing tube and shutter combina tion which are improved in that manufacture and assembly of the components is simplified and the cost thereof reduced, and further improved in that adjustment of the shutter and maintaining it in adjusted position is simplified. One form of the invention is shown in the accompanying drawings:

FIG. 1 is an elevational view of a burner equipped with a mixing tube and shutter assembly according to the present invention.

FIG. 2 is an enlarged sectional view on line 22 of FIG. 1.

FIG. 3 is an end view of the upstream end of the mixing tube and shutter assembly.

FIG. 4 is a perspective view of a shutter according to the present invention.

FIG. 5 is a view generally similar to FIG. 2 but illustrating a step in assembly of the components.

Shown in FIG. I is a gas burner having a hollow body 12 to which a mixture of fuel gas and primary air is furnished through a mixing tube 14. Burner body 12 is provided with a ring of burner ports 16. The burner is supported within a gas range or the like by means of a bracket 18.

Mixing tube 14 has an upstream end which is lobed as shown in FIG. 3 for receiving a source of fuel gas such as the outlet hood of a gas valve or a conduit 22 as is illustrated. Adjoining upstream portion 20 the mixing tube has a generaliy cylindrical portion 24 which is apertured to define primary air inlet openings 26,28. Adjacent portion 24 the mixing tube has a Venturi restriction 30 from which a mixture of fuel gas and primary air issues for delivery to burner 10. Inlets 26,28

may be identical and each is defined by circumferential side edges 32,34 34 and axial end edges 36,38.

A shutter 40 according to the invention is disposed in frictional engagement around mixing tube portion 24. Shutter 40 comprises a band of resiliently flexible metal fashioned to form a generally arcuate C-shaped body 42 which extends through an angle greater than In the structure illustrated this angle is about 280. Body 42 has circumferentially spaced edges 44,46 which define an opening 48 and body 42 has a second opening 50 disposed generally oppositely from opening 48. These openings are adjustably registrable with inlets 26,28 by turning shutter 40 on the mixing tube.

Edge 46 has a central portion which is turned radially inwardly to form a hook 52 having an exterior surface 54, an interior surface 56 and end surfaces 58. Edge 44 is turned radially outwardly to form a finger hold 60. Body 42 has axial end portions 62,64 which overlie the end edges 36,38 of inlets 26,28. Each end portion 62,64 is curved outwardly to form runner-like surfaces 66,68 adjacent its circumferential terminals. In the structure illustrated surface 66 is at the juncture of body 42 and hand hold 60 and surface 68 is adjacent a free shoulder which flanks an end 58 of hook 52.

To assemble shutter 40 on mixing tube 14 hook 52 is inserted into either primary air inlet 26 or 28 and is engaged around either side edge 32 or 34 of the selected opening. Curved surface portions 66 are engaged against mixing tube portions 24 adjacent the opposite inlet opening. A representative position of the parts is illustrated in FIG. 5 wherein hook 52 is engaged around edge 34 of opening 28 and curved surface 66 overlies end edges 36,38 of opening 26.

When manual force is exerted on body 42 in a direction upwardly and to the right as FIG. 5 is viewed, surface 66 slides clockwise around the mixing tube and body 42 flexes radially outwardly until surface 66 passes over center with respect to a diameter of the tube passing generally through edge 34. Thereafter body 42 resiliently returns radially inwardly causing shutter 40 to snap into frictional engagement around tube portion 24. Hook 52 by engagement around edge 34 provides an anchor about which body 42 of the shutter moves in a generally pivotal movement during this snap-over installation of the shutter on the tube.

In use, to adjust the effective size of primary air inlet openings 26,28 shutter 40 is simply turned manually causing openings 48,50 therein to register more or less completely with inlets 26,28. Finger hold 60 facilitates turning the shutter. Once the adjustment has been effected frictional engagement of the shutter with the exterior of tube portion 24 maintains the shutter in its adjusted position.

Because inlets 26,28 are usually formed by stamping, their end edges 36,38 frequently have sharp irregularities which would tend to interfere with turning of shutter 40 for adjustment purposes. However, the curved runner-like surfaces 66,68 tend to glide smoothly over such irregularities thereby minimizing interference to turning of the shutter.

Exterior and interior surfaces 54,56 of hook 52 provide stops which engage against side edges 32,34 of an inlet opening 26 or 28 to limit turning movement of the shutter at maximum and minimum opening adjustment of inlets 26,28. End surfaces 58 of hook 52 by engagement of end edges 36,38 of the inlet maintain the shutter in its proper axial position on tube portion 24.

Should it be necessary to remove shutter 40 from the mixing tube the shutter is turned to a position in which exterior surface 54 of hook 52 engages a side edge 32 or 34 of the inlet opening within which the hook is 'inserted. Tangential force is exerted manually on finger hold 60 causing shutter body 42 to flex resiliently open for snap-over disengagement from the tube. Here again the hook provides an anchor about which the shutter generally pivots during this snap-over movement.

Shutter 40 can be installed with hook interior 56 engaged with either edge 32,34 of either inlet 26,28. Thus, it can be installed with finger hold 60 disposed upwardly or downwardly and with opening 48 disposed toward either the right or left hand to suit various space and accessibility conditions of different installations.

We claim: 1. Shutter structure for adjusting the effective size of air inlet porting in a mixing tube for a gas burner, the porting being defined by angularly spaced side edges and axially spaced end edges, said structure comprismeans forming a generally arcuate band which turns through an angle greater than 180 and which is dimensioned and contoured to be turned in sliding frictional engagement around portions of a mixing ,tube which define such air inlet porting,

said band having edges which are angularly spaced apart to define at least one open area adjustably registrable with such porting responsive to turning thereof,

stop means extending inwardly adjacent one of said edges of said band, said stop means having first and second surfaces positioned to engage said side edges of such porting to limit turning movements of said band,

said stop means having third and fourth surfaces positioned to engage said end edges to obstruct axial movement of said band on a mixing tube, said stop means comprising hook means, said first and second surfaces comprising interior and exterior portions of said hook means, said third and fourth sur-- faces comprising end portions of said hook means, said band being resiliently radially expansible to facilitate snap-over flexing thereof to and from engagement around a mixing tube,

said first and second surfaces being cooperable with a said side edge of such porting to provide an anchor about which said band is pivotable to effect said snap-over flexing, the other of said edges of said band being turned outwardly to provide a finger hold to facilitate pivoting of said band about said anchor.

2. The structure defined in claim 1 wherein said band has an edge portion which is turned inwardly to form said hook means.

3. The structure defined in claim 2 wherein said hook means comprises a single hook extending axially between said end edges of such porting.

4. The structure defined in claim 1 wherein said band is apertured to provide a second open area generally opposite from said one open area.

5. The structure defined in claim 1 wherein said band turns arcuately through an angle of about 280 between said edges thereof.

6. The structure defined in claim 1 wherein said band has axial end portions which pass over at least portions of said end edges of such porting responsive to turning of said band on a mixing tube, said end portions having circumferential terminals adjacent said edges of said band, said terminals being curved outwardly to facilitate gliding thereof over said end edges of a mixing tube.

7. In combination, a said mixing tube and a shutter structure in accordance with claim I mounted thereon.

8. In combination, a mixing tube and a shutter structure in accordance with claim 3 mounted thereon.

9. In combination, a mixing tube and a shutter structure in accordance with claim 6 mounted thereon.

l0. Shutter structure for adjusting the effective size of air inlet porting in a mixing tube for a gas burner, the porting being defined by angularly spaced side edges and axially spaced end edges, said structure comprising,

means forming a band which is dimensioned and contoured to be turned in sliding frictional engagement around portions of a mixing tube which define such air inlet porting,

said band having portions which define at least one open area adjustably registrable with such porting responsive to turning thereof,

said band having inwardly projecting stop means with first and second surfaces positioned to engage said side edges of such porting to limit turning movements of said band,

said stop means having third and fourth surfaces positioned to engage said end edges of said porting to obstruct axial movement of said band on a mixing tube,

said band being generally arcuate and extending angularly through about 280 between spaced apart edges which define one said open area,

said band being apertured to define a second said open area generally opposite from said one open area, one of said edges of said band being turned inwardly to form a hook which defines said stop means,

the inner and outer surfaces of said hook providing said first and second surfaces, the ends of said hook defining said third and fourth surfaces said first and second surfaces being cooperable with said side edges of such porting to provide anchors about which said band is pivotable to effect snap over flexing thereof to and from engagement around a mixing tube, the other edge of said band being turned outwardly to provide a finger hold to facilitate said flexing,

said band having axial end portions which pass over portions of said end edges of such porting responsive to turning of said band on a mixing tube,

said end portions having circumferential terminals adjacent said edges of said band, said terminals being curved outwardly to facilitate gliding thereof over said end edges of such porting in a mixing tube.

1 1. In combination, a mixing tube and a shutter structure in accordance with claim 10 mounted thereon. 

1. Shutter structure for adjusting the effective size of air inlet porting in a mixing tube for a gas burner, the porting being defined by angularly spaced side edges and axially spaced end edges, said structure comprising, means forming a generally arcuate band which turns through an angle greater than 180* and which is dimensioned and contoured to be turned in sliding frictional engagement around portions of a mixing tube which define such air inlet porting, said band having edges which are angularly spaced apart to define at least one open area adjustably registrable with such porting responsive to turning thereof, stop means extending inwardly adjacent one of said edges of said band, said stop means having first and second surfaces positioned to engage said side edges of such porting to limit turning movements of said band, said stop means having third and fourth surfaces positioned to engage said end edges to obstruct axial movement of said band on a mixing tube, said stop means comprising hook means, said first and second surfaces comprising interior and exterior portions of said hook means, said third and fourth surfaces comprising end portions of said hook means, said band being resiliently radially expansible to facilitate snap-over flexing thereof to and from engagement around a mixing tube, said first and second surfaces being cooperable with a said side edge of such porting to provide an anchor about which said band is pivotable to effect said snap-over flexing, the other of said edges of said band being turned outwardly to provide a finger hold to facilitate pivoting of said band about said anchor.
 2. The structure defined in claim 1 wherein said band has an edge portion which is turned inwardly to form said hook means.
 3. The structure defined in claim 2 wherein said hook means comprises a single hook extending axially between said end edges of such porting.
 4. The structure defined in claim 1 wherein said band is apertured to provide a second open area generally opposite from said one open area.
 5. The structure defined in claim 1 wherein said band turns arcuately through an angle of about 280* between said edges thereof.
 6. The structure defined in claim 1 wherein said band has axial end portions which pass over at least portions of said end edges of such porting responsive to turning of said band on a mixing tube, said end portions having circumferential terminals adjacent said edges of said band, said terminals being curved outwardly to facilitate gliding thereof over said end edges of a mixing tube.
 7. In combination, a said mixing tube and a shutter structure in accordance with claim 1 mounted thereon.
 8. In combination, a mixing tube and a shutter structure in accordance with claim 3 mounted thereon.
 9. In combination, a mixing tube and a shutter structure in accordance with claim 6 mounted thereon.
 10. Shutter structure for adjusting the effective size of air inlet porting in a mixing tube for a gas burner, the porting being defined by angularly spaced side edges and axially spaced end edges, said structure comprising, means forming a band which is dimensioned and contoured to be turned in sliding frictional engagement around portions of a mixing tube which define suCh air inlet porting, said band having portions which define at least one open area adjustably registrable with such porting responsive to turning thereof, said band having inwardly projecting stop means with first and second surfaces positioned to engage said side edges of such porting to limit turning movements of said band, said stop means having third and fourth surfaces positioned to engage said end edges of said porting to obstruct axial movement of said band on a mixing tube, said band being generally arcuate and extending angularly through about 280* between spaced apart edges which define one said open area, said band being apertured to define a second said open area generally opposite from said one open area, one of said edges of said band being turned inwardly to form a hook which defines said stop means, the inner and outer surfaces of said hook providing said first and second surfaces, the ends of said hook defining said third and fourth surfaces, said first and second surfaces being cooperable with said side edges of such porting to provide anchors about which said band is pivotable to effect snap-over flexing thereof to and from engagement around a mixing tube, the other edge of said band being turned outwardly to provide a finger hold to facilitate said flexing, said band having axial end portions which pass over portions of said end edges of such porting responsive to turning of said band on a mixing tube, said end portions having circumferential terminals adjacent said edges of said band, said terminals being curved outwardly to facilitate gliding thereof over said end edges of such porting in a mixing tube.
 11. In combination, a mixing tube and a shutter structure in accordance with claim 10 mounted thereon. 